Rock Bolt

ABSTRACT

A rock bolt, particularly for use in mining, having an axial conduit, an anchor nut, and an anchor plate supported by the anchor nut for the purpose of placement on the rock, that is able to expand sufficiently and possess sufficient tensile strength, and also is able to be cut for the purpose of simplified separation of excavated pieces of the rock bolt. This problem is addressed in that the axial conduit is at least partially, and particularly entirely, made of metal and plastic, and the at least one component of the axial conduit made of metal and plastic serves to receive tensile forces.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to German Patent Application DE 10 2011 004 023.4, filed Feb. 14, 2011, and entitled “Gesteinsacker” (“Rock Bolt”), which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

One or more embodiments of the present invention relate to a rock bolt.

In the fields of mining and tunnel construction, rock bolts are used to prevent or slow movement in the solid rock, or to secure solid rock against larger-area flaking, thereby enabling operation without danger. In this case, two functional principles are known, and are also known in partial combination. In mechanical systems, the bolt is anchored using a friction fit, wherein mechanical rock bolts generally also have an expansion sleeve and an expanding element. In the case of chemical rock bolts, an axial conduit is connected to the substrate and/or the solid rock in a material connection using a curable mortar or an artificial resin used as a fixing agent. The rock bolts in this case are installed in the solid rock with or without pretensioning. In contrast to applications in tunnel construction, rock bolts used in mining, e.g. in underground coal mining, serve to temporarily secure the rock. This is because, in general, the temporarily secured rock will be extracted in a later work phase, and the rock bolts will then also be removed from the rock.

In mining and tunnel construction, rock bolts are used which have an axial conduit, the same being particularly designed as a hollow tube

In this case, the rock bolts are preferably made of fiberglass reinforced plastic. The plastic reinforced with fiberglass only expands to a minimal degree when the axial conduit is subjected to tensile forces in the rock, and also possesses low resistance to compression and to shearing forces. Due to the low expansion capacity of the axial conduit made of fiberglass-reinforced plastic, these rock bolts must be used in high quantities and placed closely together to prevent any movement of the substrate and to reduce the shearing forces applied to each rock bolt. Due to the low resistance to compression and shearing of the material, a large fraction of the rock bolts having the axial conduit made of fiberglass reinforced plastic are damaged and/or destroyed during the installation thereof due to the compression forces and/or shearing forces involved. In coal mining applications, such rock bolts having axial conduits which are manufactured from fiberglass reinforced plastic are used in the coal seam itself to secure the advancing section in front of a longwall section. These rock bolts are extracted together with the coal, but then cannot be removed from the coal, or can only be removed with very great difficulty. Rock bolts having an axial conduit made of steel are generally not used to secure coal seams because they cannot be cut, and/or have sharp edges following excavation of the coal. The rock bolts having an axial conduit made of steel cut up the conveyor belts or destroy other devices used in coal mining, thereby leading to high costs and interruptions. Rock bolts used in coal mining which have an axial conduit made of fiberglass reinforced plastic cause substantially no damage to conveyor belts or other devices in the mine during excavation because they can be cut easily, and therefore can be easily broken up by the excavation equipment. However, these rock bolts possess insufficient properties with respect to mechanical considerations of expansion, resistance to compression, and resistance to shearing. Rock bolts having axial conduits made of steel pose the disadvantage that they cause damage to conveyor belts and other equipment of the mine during excavation of the coal.

WO 2007/059580 A1 discloses a self-cutting rock bolt having a cutting head and an axial conduit.

BRIEF SUMMARY OF THE INVENTION

The problem addressed by one or more embodiments of the present invention is that of providing a rock bolt which possesses sufficient capacity for expansion and tensile strength, and can be cut to enable simplified separation of the excavated pieces of the rock bolt.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in greater detail below with reference to the attached illustrations, wherein:

FIG. 1 shows a longitudinal section of a rock bolt which is inserted into a bore hole, wherein the fixing agent has not yet been inserted into the space between the rock and the axial conduit,

FIG. 2 shows a longitudinal section of the rock bolt in FIG. 1, wherein the fixing agent has been inserted into the space between the rock and the axial conduit,

FIG. 3 shows a longitudinal section of an axial conduit of the rock bolt according to FIG. 1,

FIG. 4 shows a longitudinal section of a component of the axial conduit according to FIG. 3, made of metal and plastic, having a connection between the two components in a first embodiment,

FIG. 5 shows a longitudinal section of the components of the axial conduit according to FIG. 3, made of metal and plastic, having the connection between the two components in a second embodiment,

FIG. 6 shows a longitudinal section of the components of the axial conduit according to FIG. 3, made of metal and plastic, having the connection between the two components in a third embodiment,

FIG. 7 shows a longitudinal section of the components of the axial conduit according to FIG. 3, made of metal and plastic, having the connection between the two components in a fourth embodiment, and

FIG. 8 shows a longitudinal section of the components of the axial conduit according to FIG. 3, made of metal and plastic, having the connection between the two components in a fifth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

This problem is addressed by a rock bolt, particularly for use in mining, having an axial conduit, an anchor nut, and a plate supported by said anchor nut, said plate being for the purpose of placement on the rock, wherein the axial conduit is made at least partially, and particularly entirely, of metal and plastic, and this at least one component of the axial conduit which is made of metal and plastic serves to receive tensile forces.

The axial conduit of the rock bolt therefore is made of metal, particularly of steel, and of plastic. As such, the axial conduit can undergo larger expansions in the axial dimension when tensile forces are applied thereto, such that the rock bolt is also by design a directional anchor. In this way, movements which occur in the secured rock can be secured against in an improved manner. In addition, the axial conduit of the rock bolt can be easily broken up and/or separated by mining machines in the mining applications, particularly in coal mining applications, such that damage can be substantially prevented to the technical equipment of the mining operation.

The rock bolt particularly is made, in one inner segment of the axial conduit, at least partially, and particularly entirely, of metal and plastic.

In a further embodiment, the axial conduit has a front end and a rear end, and the inner segment is distanced from the front and the rear ends by a gap of at least 5%, 10%, or 20% of the total length of the axial conduit. Therefore, the design of the rock bolt as made of metal and plastic preferably does not involve the region of the rock bolt in the proximity of the front and the rear ends.

In a further embodiment, the rock bolt is constructed in multiple sections of components made of plastic and metal. The at least one component of the rock bolt made of plastic and the at least one component of the rock bolt made of metal are initially produced separately, and are connected to each other during the manufacture of the rock bolt.

One component made of metal and one component made of plastic are preferably arranged in an alternating manner along the longitudinal dimension of the rock bolt, and/or the rock bolt made of of metal has no sheathing made of plastic, particularly on the inner segment, and the at least one component made of plastic is particularly not a sheathing of the at least one component made of metal.

In one variant, the plastic is reinforced plastic, particularly plastic reinforced by fiberglass, and the metal is steel.

The at least one plastic component is made advantageously of at least 50%, 70%, or 90% plastic, and particularly is entirely plastic, and/or the at least one component is made of at least 50%, 70%, or 90% metal, and particularly is entirely metal.

In a further embodiment, the rock bolt is made of at least 50%, 70%, or 90%, and particularly is made entirely of, plastic in a first segment thereof, particularly in the inner segment as a cross-section which is perpendicular to the longitudinal axis of the rock bolt, and in a second segment, particularly in the inner segment as a cross-section which is perpendicular to the longitudinal axis of the rock bolt, the rock bolt is made of at least 50%, 70%, or 90%, and particularly is made entirely of, metal.

The components are particularly connected to each other using an inner or outer plastic sheath, and/or fibers of the reinforced plastic are arranged on the metal components. The fibers are particularly saturated with a matrix material and then cured, and the plastic component is connected to the metal component using the fibers, and/or the inner diameter of one component corresponds substantially to the outer diameter of another component, such that the other component is arranged coaxially inside the component, and both components are connected to each other by an adhesive bond, and/or one component has an inner threading and another component has an outer threading, such that both components are screwed into each other via the inner and outer threadings, and/or the outer diameter of one component and the inner diameter of another component, preferably sectionally, are substantially the same, and the other component is partially slid over the component on an overlap region thereof, and then both components are connected to each other by a sheath which is pressed onto the outside of the same, said sheath particularly made of metal, e.g. steel.

In a further embodiment, the axial conduit is designed as a hollow tube.

In a complementary variant, the axial tube encloses an interior space, and the rock bolt has a fixing agent arranged in the interior for the purpose of establishing a material, fixed connection of the axial conduit to the rock, a movable piston arranged in the interior of the fixing agent and outside the axial conduit when the axial conduit is arranged in a bore hole in the rock, and at least one system for moving the piston. The rock bolt is therefore a chemical rock bolt.

In a further variant, a rear end of the axial conduit is closed by a cap, and the axial conduit and/or the cap have at least one opening for conveying the fixing agent out of the interior space enclosed by the axial conduit.

In a further embodiment, a mixer is arranged between the fixing agent and the at least one opening for the purpose of mixing the fixing agent, particularly the two components thereof, prior to the fixing agent exiting the at least one opening.

The rock bolt particularly has an expansion sleeve and an expansion element. The rock bolt is therefore a mechanical rock bolt.

Rock bolts are preferably also rock anchors.

In a complementary embodiment, the fixing agent, particularly an artificial resin or mortar, has two components, e.g. one adhesive component and one curing component.

The two components are preferably each arranged in separate pouches. In this case, any device which contains the two separate components is considered a pouch. For example, a cartridge or a different type of container can be contemplated.

In a further embodiment, the rock bolt has a drilling head, particularly in the region of the front end or on the front end of the axial conduit. The rock bolt is therefore a self-cutting rock bolt.

Referring now to the Figures, a rock bolt 1 designed as a directional anchor 2 is used in mining applications for the purpose of temporarily securing the rock in a gallery. The rock bolt 1 has an axial conduit 3 which encloses an interior space 4. The rock bolt 1 is a chemical rock bolt 1, meaning that the axial conduit 3 can be attached to the rock 28 in a material connection using a fixing agent 5 arranged in the interior space 4. For this purpose, a bore hole 29 is constructed in the rock 28, and the rock bolt 1 is then inserted into the bore hole 29. This process is portrayed in FIG. 1, prior to the fixing agent 5 being pressed out into a space between the axial conduit 3 and the rock 28. In FIG. 2, the rock bolt 1 which is attached by a material connection to the rock 28 is illustrated. The fixing agent 5 in this case is an artificial resin 6 which has an adhesive component 7 and a curing component 8. The adhesive component 7 is contained in a first pouch 9, and the curing component 8 is contained in a second pouch 10. Both pouches 9, 10 are contained in the interior space 9.

The interior space 4 has a hydraulic chamber 17 which is closed by a ring piece 20 in the region of the outer, rear end 37 of the axial conduit 3. The ring piece 20 has a hydraulic bore hole 19. In addition, the hydraulic chamber 17 is bounded by a piston 11 in the region of a different, inner, front end 36. The inner, front end 36 of the axial conduit 3 is closed by a cap 23 having an opening 24. The fixing agent 5 can flow out of the interior space 4 of the axial conduit 3 through the opening 24 and out into the space, particularly the annular space, between the rock bolt 3 and the rock 28. In this case, a mixer 25 is arranged on the opening 24, and the fixing agent 5 must necessarily flow first from the two pouches 9, 10 through the mixer 25, due to the geometrical arrangement of the mixer 25 in the interior space 4, then the fixing agent 5 flows out through the opening 24. In this case, the mixer 25 has devices, by way of example a corresponding geometry, such that the fixing agent 5 flows through the mixer 25 in a circuitous or looping manner, achieving a mixing of the adhesive component 7 and the curing component 8 of the artificial resin 6 prior to the same flowing out through the opening 24.

An anchor nut 14 is screwed onto the outer threading 18 in the region of the outer, rear end 37 of the axial conduit 3, the same having an outer threading 18, wherein said anchor nut 14 has an inner threading and an anchor plate 15 lies on the anchor nut 14. The anchor plate 15 in this case has a plate boring 13 with no inner threading, and the axial conduit 3 is arranged inside said plate boring 13. In this way, pressure can be applied by the rock 28 according to the illustration in FIG. 2 onto the anchor plate 15. This pressure is transmitted by the anchor plate 15 to the anchor nut 14, and then from the anchor nut 14 to the axial conduit 3, such that a tensile force acts on the axial conduit 3. This tensile force is transmitted to the rock 28 by the axial conduit 3, in a material connection with the fixing agent 5 on the outside of the axial conduit 3.

For the purpose of introducing the fixing agent 5 into the space between the axial conduit 3 and the rock 28, a piston 11 is moved inward, meaning that, according to the illustration in FIG. 1, the piston 11 moves upward. In this manner, the first and the second pouches 9, 10 are destroyed by the piston 11, such that the adhesive component 7 and the curing component 8 move, and the fixing agent 5 is pressed through the mixer 25 and through the opening 24 into the space between the axial conduit 4 and the rock 28 due to the shrinking volume of the interior space 4 between the piston 11 and the cap 23, and the fixing agent 5 subsequently cures. For this purpose, a hydraulic fluid, e.g. water, is pumped under high pressure into the hydraulic chamber 17 through the hydraulic bore hole 19, thereby moving the piston 11. The hydraulic chamber 17 and the hydraulic bore hole 19 are therefore a structure 12 for moving the piston 11.

In FIG. 2, the fixing agent 5 is already fully extruded into the space between the axial conduit 3 and the rock 28, meaning that the axial conduit 3 is attached to the rock 28 in a material connection, particularly by using adhesive bonding. In the state of installation illustrated in FIG. 2 in this case, the axial conduit 3 is substantially entirely arranged in the interior space 4, meaning that only a small fraction of the axial conduit 3, by way of example less than 10% or 5%, is present outside the interior space 4. In this way, when the rock bolt 1 is installed, very little space is required in the work space 30 in the mining gallery. In the state of the rock bolt illustrated in FIG. 2, the anchor plate 15 rests on the rock 28, and can therefore receive compression forces. In addition, shearing forces applied perpendicular to a longitudinal axis 38 of the axial conduit 3 can also be received by the rock bolt 1, and the rock 28 can be additionally secured in this manner.

In FIG. 3, a part of the axial conduit 3 is illustrated in a longitudinal section as a hollow tube. The axial conduit 3 is made of components 26 made of metal, particularly steel or a steel alloy, and components 27 made of plastic, particularly a plastic which is reinforced by fiberglass. In this case, these components 26, 27 made of metal and plastic are arranged in an alternating configuration along the direction of a longitudinal axis 38 of the axial conduit 3. In FIG. 3, the type of connection between the component 26, 27 is not illustrated. The fibers 32 of the fiberglass reinforced plastic of the components 27, said fibers 32 being not illustrated, have fibers 32 which are oriented in the direction of the longitudinal axis 38 for the purpose of receiving tensile forces exerted on the axial conduit 3, and have fibers 32 which are oriented at an angle to the longitudinal axis 38, by way of example perpendicular thereto or at an angle of approximately 45° to the direction of the longitudinal axis 38. The latter fibers 32 constitute cross fibers and can receive torsional loads exerted on the axial conduit 3. The components 26 made of metal have a roughened surface 22 on the outer side thereof.

In FIGS. 4 to 8, different embodiments of the connection of the components 26, 27 are illustrated. In the first embodiment, according to FIG. 4, a plastic sheath 31 is applied by using injection molding to both the components 26 made of metal and the components 27 made of plastic. In this way, both components 26, 27 are connected to each other.

In the second embodiment, according to FIG. 5, fibers of the fiberglass reinforced plastic of the components 27 are applied to the outside of the components 26 made of metal. These fibers in this case are saturated with a matrix material, for example an artificial resin, and then cured. In this way, it is possible to produce a load-bearing connection to the component 26 made of metal, i.e. a steel component.

In this case, these fibers 32 are laid out as both longitudinal fibers and cross fibers.

In FIG. 6, a third embodiment of the connection between the components 26, 27 is illustrated. The inner diameter of one component 26 corresponds in this case substantially to an outer diameter of another component 27. Thus the inner and outer diameters in this case substantially comprise a difference of less than 10%, 5%, 2% or 1%. In this way, the component 27 as a plastic part can be inserted coaxially into the component 26 as a steel part. By using adhesive bonding 33, both a material connection and a positive-fit connection can be produced between the components 26, 27.

In the fourth embodiment illustrated in FIG. 7, the component 26 has an outer threading, and the component 27 has an inner threading, both indicated as the threading 34. In this way, the two threadings 34 can be screwed together, thereby producing a connection between the two components 26, 27.

In FIG. 8, a fifth embodiment of the connection between the components 26, 27 is illustrated. The fibers 32, particularly the fibers laid out as longitudinal and cross fibers, are applied in this case to the outside of the component 26. These fibers 32 applied to the outside of the component 26 are pressed or clamped to each other by using a sheath 35, particularly a steel sheath 35. The sheath 35 is therefore pressed onto the fibers 32 or is designed with a conical shape and/or is screwable, for the purpose of generating a radial pressure between the fibers 32 and the outer side of the component 26 made of metal.

The axial conduit 3 therefore has, in alternating sequence, the steel parts 26 and/or components 26 made of steel, and the plastic parts 27 and/or the components 27 made of plastic. After the rock bolt 1 is fixed in the bore hole 29 and/or on the rock 28, the tensile forces are received by the axial conduit 3.

In this case, the components 26 made of metal, particularly of steel, have high expansion upon the exertion of tensile forces, such that a large overall expansion occurs in the axial conduit 3 when high tensile forces are exerted on the same. This happens because a substantial fraction of the axial conduit 3 is made of the components 26. In this case, the components 26 comprise at least 30%, 50%, or 70% of the total expansion of the axial conduit 3, preferably in the direction of the longitudinal axis 38. In this way, the rock bolt 1 is also a directional anchor, and as such has a sliding function such that small movements in the secured rock 28 can be received due to the length modification of the axial conduit 3 in the form of elongation. As such, movements of the rock 28 are permitted by the rock bolt 1. In this way, it is possible to substantially prevent the axial conduit from breaking unexpectedly.

The rock bolt 1 will be used substantially in mining, particularly coal mining. In the case of application in mining, the rock bolt 1 is used for the purpose of temporarily securing the solid rock 28, and particularly coal. The coal is excavated using a shearer or a coal plow. During this excavation, the rock bolts 1 are also removed with the coal and/or in the rock 28, and can be broken up by the shearer or the coal plow, and thereby transported away, because the components 27 made of plastic can be easily separated by the shearer or the coal plow. In this way, following excavation, only small partial pieces of the axial conduit 3 appear, and these can be easily transported by the conveyor system. Due to the fraction of metal also present in the components 26, the same can be easily separated by a magnetic separator. Moreover, it is also possible to separate the bolt pieces made of metal from the coal in a wash plant, because the two materials have largely different densities.

In a further, not illustrated, embodiment of the rock bolt, the rock bolt substantially comprises only the axial conduit 3, the anchor nut 14, and the anchor plate 15. In this case, the axial conduit 3 is not designed as a hollow tube, but rather as a solid profile.

When this rock bolt 1 is inserted into a bore hole 29, a fixing agent 5 is first inserted into the bore hole 29, and the axial conduit 3 is then inserted into the bore hole 29. In this manner, the fixing agent 5 is distributed in a space between the axial conduit 3 and the bore hole 29. In this case, the fixing agent 5 can also have been inserted into the bore hole 29 in at least one pouch 9, 10 prior to the insertion of the axial conduit 3.

As a whole, the rock bolt 1 according to an embodiment of the invention involves substantial advantages. Due to the use of metal, the axial conduit 3, having components 26, 27 made of metal and plastic, comprises a sufficiently high expansion in the event of tensile forces exerted on the same following the installation of the rock bolt 1 into the bore hole 29, such that it is possible to substantially prevent an unexpected break of the bolt. In addition, the axial conduit 3 can receive large compression forces exerted during the insertion of the same into the bore hole 29. Both the components 26 made of metal and the components 27 made of plastic have high resistance to compression, meaning that said components 26, 27 can receive large compression forces exerted in the dimension of the longitudinal axis 38. In the case of rock excavation 28, particularly of coal, the axial conduits 3 can be easily severed due to the exclusive use of components 27 made of plastic along the longitudinal dimension 38. In this way, it is possible to reduce damage to the excavation equipment in the mine.

While particular elements, embodiments, and applications of the present invention have been shown and described, it is understood that the invention is not limited thereto because modifications may be made by those skilled in the art, particularly in light of the foregoing teaching. It is therefore contemplated by the appended claims to cover such modifications and incorporate those features which come within the spirit and scope of the invention. 

1. A rock bolt, said rock bolt including: an axial conduit; an anchor nut; and an anchor plate supported by the anchor nut, for the purpose of placement on the rock, wherein the axial conduit is made at least partially of both metal and plastic, wherein at least one component of the axial conduit, said component being made of metal and plastic, serves to receive tensile forces.
 2. A rock bolt according to claim 1 wherein the axial conduit, on an inner segment of the axial conduit, is made at least partially of both metal and plastic.
 3. A rock bolt according to claim 2, wherein the axial conduit has a front end and a rear end, and the inner segment is spaced from the front and the rear ends at a distance of at least 5%, 10%, or 20% of the total length of the axial conduit.
 4. A rock bolt according to claim 3 wherein the axial conduit is constructed in multiple parts from components made of either plastic and metal.
 5. A rock bolt according to claim 4, wherein on the axial conduit one component made of metal and one component made of plastic are arranged in alternating sequence along the dimension of a longitudinal axis of the axial conduit,
 6. A rock bolt according to claim 4, wherein the axial conduit is made of metal on the inner segment thereof, and does not have a sheath made of plastic, and the at least one component made of plastic is not a sheath of the at least one component made of metal.
 7. A rock bolt according to claim 6, wherein the plastic is reinforced with fibers, and the metal is steel.
 8. A rock bolt according to claim 7, wherein said fibers are fiberglass
 9. A rock bolt according to claim 4, wherein the at least one component made of plastic is made of at least 50% plastic.
 10. A rock bolt according to claim 4, wherein the at least one component made of metal is made of at least 50% metal.
 11. A rock bolt according to claim 1, wherein in a first section which is perpendicular to a longitudinal axis of the axial conduit, on the inner section, the axial conduit is made of at least 50% plastic.
 12. A rock bolt according to claim 1, wherein in a second section which is perpendicular to a longitudinal axis of the axial conduit, on the inner section, the axial conduit is made of at least 50% metal.
 13. A rock bolt according to claim 4 wherein the components are connected to each other using an inner or outer plastic sheathing.
 14. A rock bolt according to claim 4 wherein fibers of the plastic which is reinforced with the fibers are arranged on the component made of metal, the fibers are saturated with a matrix material and cured, and the component made of plastic is connected to the component made of metal using the fibers.
 15. A rock bolt according to claim 4 wherein the inner diameter of one component corresponds substantially to the outer diameter of another component, such that the other component is arranged axially inside the component, and the two components are connected using an adhesive bond to each other, and one component has an inner threading, and another component has an outer threading, such that both components are axially screwed into each other on the inner and outer threadings thereof, and the outer diameter of one component and, at least sectionally, the inner diameter of another component are substantially the same, and the other component is partially slid over the one component on an overlap region thereof, wherein the two components are connected to each other using a sheathing pressed onto the outside thereof on the overlap region, and said sheathing is made of metal.
 16. A rock bolt according to claim 1, wherein the axial conduit is designed as a hollow tube.
 17. A rock bolt according to claim 1, wherein the axial conduit encloses an interior space, and the rock bolt has a fixing agent arranged in the interior space for the purpose of fixing the axial conduit on the rock with a material connection, a moving piston arranged in the interior space for the purpose of conveying the fixing agent to the outside of the axial conduit when the axial conduit is arranged inside a bore hole in the rock, and at least one structure for moving the piston.
 18. A rock bolt according to claim 17, wherein a rear end of the axial conduit is closed by a cap, and the axial conduit and/or the cap have at least one opening for the purpose of conveying the fixing agent out of the interior space enclosed by the axial conduit.
 19. A rock bolt according to claim 17, wherein a mixer is arranged between the fixing agent and the at least one opening for the purpose of mixing the fixing agent prior to the fixing agent discharging from the at least one opening.
 20. A rock bolt according to claim 1, wherein the rock bolt has an expansion sheath and an expanding element. 